Provider education · Metabolic
Hemoglobin A1c: interpretation and ordering cadence.
By New Century Labs · Last updated July 6, 2026
Hemoglobin A1c summarizes glycemic status over months in a single value, which is exactly why it needs careful reading. This guide is for the ordering clinician: what A1c reflects, where it misleads, and how often retesting makes sense.
What the test measures
Hemoglobin A1c reflects the fraction of hemoglobin that has become glycated through exposure to blood glucose. Because red cells circulate for roughly the lifespan of the cell, A1c integrates average glucose over the preceding two to three months rather than the moment of the draw. That gives it a distinct role from a single glucose reading: it describes a trend, not a snapshot, and it does not require fasting.
Interpreting the result
The reference range applied by our national laboratory network is <5.7% of total hemoglobin. Values are read as a reflection of longer-term glycemic status, with higher percentages indicating higher average glucose over the measured window. A1c is used to assess glycemic control and to support screening and monitoring conversations; it is one input into a clinical picture, not a diagnosis on its own. Diagnostic thresholds and treatment targets are set by clinical guideline and by the individual patient's context.
Where A1c can mislead
Because A1c depends on the hemoglobin it measures and on red cell lifespan, conditions that alter either can distort the result. Per the assay's own guidance, hemoglobin A1c is observed to be lower in healthy pregnant women than in healthy non-pregnant women, and medical conditions associated with high red blood cell turnover are associated with lower hemoglobin A1c values. In those settings the number can understate true average glucose, and clinicians may consider corroborating measures. Interpretation always belongs with the ordering provider.
At a glance · Ordering logistics
- Quest order code
- 496
- Fasting
- No
- Specimen
- Whole blood
- Typical turnaround
- Typically about one business day
- Reference range
- <5.7% of total hemoglobin
Performed through our national laboratory network. Draw access is nationwide; results return to the ordering provider.
Ordering cadence
Because A1c reflects a two-to-three-month window, retesting more often than that window rarely adds information, since a fresh value cannot yet reflect a recent change. Clinicians commonly space monitoring to match the pace of the clinical question: a longer interval for stable, at-goal patients, and a shorter one when a management change is being assessed or control is shifting. The no-fasting, single-day turnaround makes A1c convenient to fold into a routine visit. The interval and its interpretation remain the provider's decision, and nothing here is a treatment recommendation.
Practical notes for ordering
A1c uses a whole blood specimen and needs no fasting, so it can be drawn at any time of day and paired with other routine work. Turnaround is typically about one business day. Patients complete the draw at CLIA-certified sites nationwide, and results return to the ordering provider. For the full set of provider guides, return to the learning resources hub.
Next step
Add A1c monitoring to your practice.
Set up ordering through our national laboratory network, with nationwide patient draw access.